<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
</head>

<body>
    <div class="box">
        <div>adsfasdf</div>
        <p>sfasdf</p>
        <span>asdfa</span>
        <div>
            <span class="aa">asdfa</span>
        </div>
    </div>


    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
    <script>
        var $box = $('.box');
        // 查找$box的后代元素, 类名为aaa
        var $aa = $box.find('.aa');
        console.log('$aa', $aa);

        // 查找$box所有子代元素
        var $children = $box.children();
        console.log('$children', $children);
    </script>
</body>

</html>